Prevalence of age-related macular degeneration among the elderly.

Background: Age-related macular degeneration (AMD) is the leading cause of visual impairment and blindness in elderly population in the developing countries. Previous epidemiological studies revealed various potential modifiable risk factors for this disease. The purpose of this study was to evaluate the prevalence of AMD among elderly living in Babol, North of Iran. Methods: The study population of this cross-sectional study came from the Amirkola Health and Ageing Project (AHAP), the first comprehensive cohort study of the health of people aged 60 years and over in Amirkola, North of Iran. The prevalence of AMD was estimated and its risk was determined using logistic regression analysis (LRA) with regard to variables such as smoking, hyperlipidemia, hypertension and diabetes. Results: Five hundred and five participants with mean age of 71.55±5.9 (ranged 60-89) years entered the study. The prevalence of AMD was 17.6%. There was a significant association between AMD and smoking (P<0.001) but no association was seen with AMD and age, level of education, history of hyperlipidemia, hypertension and diabetes. Multiple LRAs revealed that smoking increased AMD by odds ratio of 5.03 (95% confidence interval 2.47-10.23 p<0.001) as compared to nonsmokers Conclusion: According to our findings, the prevalence of AMD was relatively high and smoking increased the risk of AMD in the elderly population.

A ge-related macular degeneration (AMD) is the leading cause of visual impairment and blindness in elderly population in developing countries (1). Previous systematic review studies revealed that age-specific estimates revealed a prevalence of early AMD which was more common in European ancestry (%8.8) (2) than Asians (%6.8) (3) but this discrepancy was not seen in late AMD. Recent reports have revealed that AMD in any age is more common in European countries than Asians and Africans. As the prevalence of the disease is likely to increase in future decades as the global population exponential ageing pattern, the global burden of the AMD was estimated to reach the projected number of 196 million people in 2020 and 288 million in 2040 (4). It is hypothesized that a dysregulation in the activation of alternative pathway of complement system leads to retinal damage resulting in AMD (5)(6). As there is no effective treatment for all types of AMD, identifying modifiable risk factors is of great importance (7). Numerous epidemiological studies revealed various potential risk factors for AMD. with AMD in some studies (8)(9)(10)(11)(12). Smoking has been identified as the most consistent and major modifiable risk factor for AMD (13)(14)(15).
The growing trend of population ageing will increase the burden of AMD-related ocular morbidity which resulted in dominant impairment in quality of life, emotional management and functional independence (16)(17)(18).
Therefore, realizing the burden of the disease and prevalence of the associated risk factors is necessary for making program and policy. Although there have been several population-based studies of AMD world-wide; but there was no data from elderly Iranian. On the other hand, scarce information is available about the health of older people in Iran. We aimed to determine the prevalence of AMD and assess the frequency of several AMD risk factors in an Iranian elderly population. This study was first ophthalmologic report of the Amirkola Health and Ageing Project (AHAP).

Methods
This cross-sectional study was a part of the Amirkola  As described in table 2, logistic regression analysis was performed to assess the risk factors associated with AMD among the study population by the rejection of confounding factors. When adjusted for possible confounders, it demonstrated that men who smoked had a higher risk of AMD of (multivariate adjusted OR=5.03; 95% CI, 2.47-10.23); P<0.001) compared with those that never smoked. Also, men who were nearly 2 times more likely to have AMD (multivariate adjusted OR=2.23; 95% CI, 1.09-4.57); P=0.02) than women. There is no association between AMD and other risk factors e.g. diabetes, hyperlipidemia and hypertension in our study population (table2).  (7).

Table2. Multivariate logistic regression analysis for determining the predictors of AMD in an elderly population of
According to multivariate analysis, in our population men were nearly 2 times more likely to have AMD.
Unfortunately, all smokers in our study population were men which may affect the statistical power and the weak association for of this variable. Although the substantial higher smoking rate in Asian men than women is wellknown (34) but the main reason for this discrepancy here, is because of the culture and religious circumstances in our region in which smoking among women is considered beyond normal in those ages.
The major limitation of the study is the relatively small number of participants in our study population. In addition, because the AHAP cohort sampling scheme was not designed to be statistically representative of the Iranian population, thus the estimation of the prevalence of AMD is not directly generalizable to the Iranian population. On the other hand, we did not include institutionalized individuals, and we excluded participants without any gradable fundus photographs which may cause the underestimation of AMD prevalence.
Although we knew that the Iranian population consists of different ethnic groups and the probable genetical variations could affect the prevalence in different areas.
Conclusion: For the first time, our study documented the AMD prevalence in such population in Iran. Higher prevalence and increased risk of AMD seen among smokers underlined the need for future studies on this cohort to provide valuable data on AMD and the possible interaction between the epidemiological characteristics of this region.
AMD is considered as the most common etiology of severe visual impairment among the elderly, but the treatment approach is still the matter of controversy, thus, reducing the risk of this disease via preventive strategies seemed to be another available choice.